Aust not on Trump's top relationships list

US President Donald Trump has listed at a raucous rally to mark his 100 days in the White House the countries he has built great relationships with - and Australia didn't receive a mention.

But that could change after Australian Prime Minister Malcolm Turnbull jets to New York to meet with Mr Trump on Thursday.

Mr Trump was back in his comfort zone on Saturday, surrounded by placard waving faithful at the Pennsylvania Farm Show Complex & Expo Center for the rally.

"We have built such strong foundations with the leaders of foreign countries and we are set to rock," Mr Trump told the packed crowd that chanted "USA, USA, USA", "lock her up" and "drain the swamp" during his speech.

"But we have great relationships with Germany and Japan and China and so many others, the UK.

"Such great relationships."

Mr Turnbull will spend less than two days in New York, with a 75th anniversary Battle of the Coral Sea commemorative dinner and a bilateral meeting with Mr Trump on the agenda.

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The meeting follows the leaders' acrimonious January 28 phone call where Mr Trump was upset about the asylum-seeker deal Mr Turnbull struck last year with then President Barack Obama.

Mr Trump has said he will honour the deal.

In his Pennsylvania speech he returned to many of his popular pre-election talking points.

That included his decision, just three days into his presidency, to withdraw the US from the Trans-Pacific Partnership with Australia, New Zealand, Japan and eight other Pacific nations.

"To protect our jobs and economic freedom I immediately withdrew the United States from the horrible, disastrous, would have been another NAFTA (North American Free Trade Agreement) but worse Trans-Pacific Partnership," Mr Trump said.

"That would have taken your jobs in Pennsylvania.

"That I can tell you.

"That was a total hoax."

In other comments that would have been closely watched in Canberra, Mr Trump said he would make a decision in the next two weeks on America's support for the Paris Agreement on climate change.

Mr Trump appears to be leaning toward walking away from the agreement, describing it as "the one-sided Paris climate accord" and telling the rally the US has paid billions of dollars while China, Russia and India "have contributed, and will contribute, nothing".

Mr Trump said full compliance with the agreement could shrink America's Gross Domestic Product by $US2.5 trillion over a 10-year period and "that means factories and plants closing all over our country".

"I'll be making a big decision on the Paris accord over the next two weeks and we will see what happens," Mr Trump said.

He chose to address the rally instead of attend Saturday's White House Correspondents' dinner, becoming the first president since Ronald Reagan in 1981 not to attend.

Mr Reagan was recovering from being shot in an assassination attempt.

Mr Trump described cable TV news channels CNN and MSNBC as "fake news" and said reporters from the outlets "would love to be with us right here tonight".

"But they are trapped at the dinner which will be very, very boring," he said.